1. Field of the Invention
The subject invention relates to the use of foam inhibitors in printing pastes which are oil-in-water emulsions or aqueous emulsions. The foam inhibitors are mixtures of (a) monoalkylphosphates with (b) aliphatic esters or high boiling hydrocarbons.
2. Description of the Prior Art
Printing pastes of all types tend to foam more or less during printing particularly when they contain dispersing and/or emulsifying agents which is usually the case. The foaming must be prevented by the addition of foam inhibitors if uniform and sharp prints are to be obtained. Several such agents are known, for instance, fatty acid esters of alkyl ethers (see German Pat. No. 2,114,609 and German Published Application No. 2,143,988). However, it is difficult to reproduce them on an industrial scale and products are, therefore, obtained with varying foam inhibiting effects. Silicone-based foam inhibitors are also used but they are not satisfactory in every respect.
Swiss Pat. No. 561,322 describes esters of carboxylic acid with 4 to 18 carbon atoms respectively in the alkyl radical of the alcohol and the acid, preferably in mixtures with tris-C.sub.4-8 -alkyl phosphates, particularly tributyl phosphate, as foam inhibitors in optical brighteners of synthetic fibers. The use of these foam inhibitors in printing pastes is not possible. If triisobutylphosphate is used in printing pastes with oil-in-water emulsion based thickeners, they are absorbed into the oil phase rendering it worthless, and if used in pigment printing pastes, the triisobutylphosphate acts like a plasticizer upon the binder so that the print has a tacky texture and even becomes sticky when larger quantities are used. Moreover, higher trialkyl phosphates such as trioctyl phosphate are difficult to obtain and cannot be procured in the market place at least not on an industrial scale.
Because of the problems associated with using these foam inhibitors, there is a need to develop foam inhibitors for textile printing which overcome the described drawbacks of the known defoamers and are easily accessable.